The present invention relates to an apparatus and method for biological purification of wastes. More particularly, the invention is directed to an apparatus and method for treatment of wastes, such as grease and other contaminants contained in waste water streams, ground water, soil, etc., by introducing living organisms to biodegrade the wastes.
Wastes, under normal conditions, are gradually broken down or biodegraded by indigenous microorganisms in the environment. However, biodegradation reactions are often hindered by environmental fluctuations such as changes in temperature, pH, salinity, water and air supply, etc. For example, wastes such as fat and grease are biodegraded by microorganisms to fatty acids and glycerol. In the presence of oxygen the fatty acids are further metabolized with the end product being carbon dioxide. Glycerol is also metabolized as an efficient energy source.
Waste water systems, for example those in the food service industry, typically incorporate a grease trap to trap grease and other contaminants from the passing flow of waste water and to store such contaminants for eventual removal from the trap. Typically, the grease trap is accessed periodically and the contaminants removed for eventual disposal. Grease and other contaminants often build up very quickly in such traps. If they are not removed in a timely fashion, the ability of the trap to operate efficiently, or at all, is seriously affected. When a trap is no longer functional, the contaminants will bypass the trap and flow into areas which are intended to be free from these contaminants. Specifically, the contaminants will either clog up the waste water system or will flow into the municipal sewer system in violation of local ordinances or state laws. Most grease traps require relatively large compartments, particularly if the associated food service facility operates on a large volume.
A variety of approaches have been developed to increase the required period between subsequent cleanings of a grease trap by increasing the biodegradation by microorganisms of grease in the trap. One approach to enhancing biodegradation of grease in a grease trap is to introduce chemicals or nutrients to the trap to aid naturally occurring bacteria or microorganisms in the trap. For example, U.S. Pat. No. 5,340,376 granted to Cunningham discloses a controlled-release nutrient source that adds nutrients at low levels to a bioremediation environment to enhance microorganism growth and activity and promote the effectiveness of the bioremediation in removing environmental contaminants. The nutrients are in the form of coated solid particles, each having a core of water soluble microorganism nutrients encapsulated in a release rate-controlling coating. The effectiveness of bioremediation of wastes by enhancing the growth of naturally occurring bacteria or microorganisms with the introduction of a controlled-release nutrient source is still hindered due to environmental fluctuations such as changes in temperature, pH, salinity, water and air supply, etc.
Another approach to enhancing biodegradation of grease in a grease trap is to introduce a structure upon which indigenous microorganisms can bind and grow, and thus effectively remain in the grease trap. For example, U.S. Pat. No. 4,925,564 and U.S. Pat. No. 4,670,149 both granted to Francis disclose a bacterial incubator device having an enclosure with a foraminous wall structure packed with high surface area elements such as spherical packing of a shape or size to multiply the solid bacterial growth surface area in a grease trap. The incubator is positioned at the interface of floating grease and water. Similarly, the effectiveness of bioremediation of wastes by enhancing the growth of naturally occurring bacteria or microorganisms with the introduction of a support structure is often hindered due to environmental fluctuations such as changes in temperature, pH, salinity, water and air supply, etc.
Still another approach to enhancing biodegradation of grease in a grease trap is to introduce additional microorganisms into the grease trap. For example, U.S. Pat. No. 5,271,829 granted to Heppenstall discloses a treatment system for waste water which includes a dispenser for introducing treatment material, a solution of bacteria, into a grease trap for the purpose of digesting the grease which is separated from waste water as it flows through the grease trap. The dispenser includes a housing having a compartment for holding a quantity of grease digesting material and a dispensing opening at the lower end of the compartment. A restricter is located at the dispensing opening permitting the digesting material to pass at a constant restrictive rate from the dispensing opening to the grease to be treated in a chamber of the grease-trap. The grease digesting material in the dispenser will naturally go through a four phase growth cycle (i.e., lag, exponential, stationary, and death, further described in detail in a Bacterial Growth Section below) which limits its effectiveness of enhancing the biodegradation of grease on an extended or continuous basis.
Another example of introducing additional microorganisms in to a grease trap is U.S. Pat. No. 5,225,083 granted to Pappas, et al. Pappas, et al. discloses a simple method that includes adding endemic bacterial microorganisms to one or more of the drain lines for ultimate introduction into the grease trap and biodegrading grease. Depending on the bacterial microorganisms growth cycle phases, the effectiveness of the biodegradation of grease by the microorganisms will vary.
Another approach to enhancing biodegradation of grease in a grease trap is to introduce enzymes into the grease trap to solubilize the grease. For example U.S. Pat. No. 4,940,539 granted to Weber discloses a grease trap comprising a housing having an inlet to receive waste water containing grease and an outlet. The waste water within the housing is heated by an electric heating element which is immersed in the waste water and the heating element is controlled by a thermostat to maintain a desired temperature of the water within a given range. An aqueous composition containing a mixture of enzymes and bacterial spores is introduced into the housing into contact with the waste water. The enzymes solubilize the grease while the bacteria spores biodegrade the grease. However, the ability of the bacteria to biodegrade waste will be delayed in that the bacterial spores first enter a lag phase requiring a period of time before entering an exponential growth phase in which to begin biodegradation of the waste.
Another example, U.S. Pat. No. 4,882,059 granted to Wong, et al. discloses a method for solubilizing particulate materials in waste water which comprises the steps of cultivating aerobic bacteria in the presence of oxygen in an activator solution containing a food source until the level of the food source drops below a predetermined level causing the bacteria to begin producing increased amounts of enzymes and thereafter contacting the activated bacteria and enzymes with the particulate materials under conditions which solubilize the waste. Another example, shown in U.S. Pat. No. 5,171,687 granted to Moller, et al., discloses an apparatus for culturing and delivering microbes for waste treatment in a flow system. The apparatus includes a container having a first and second chambers. The first chamber is maintained in a nutrient rich environment for the source microbial matter supported therein while the second chamber is nutrient deficient. Water is introduced into the first chamber at a predetermined rate and flows through an outlet into the second chamber. The outlet of the second chamber is directed to a flow system benefiting from the activity of the microbial matter. In both Wong and Moller, et al., it is believed that starving the bacteria of nutrients activates enzyme production therein to aid in solubilizing particulate materials in waste water. Although, the enzymes aid in solubilizing the grease, the bacteria will be ineffective in biodegrading the solubilized grease in that the bacteria being nutrient deficient will enter a stationary phase (if not death phase) necessitating that the bacteria enters a lag phase, requiring a period of time before the bacteria enters an exponential growth phase in which to begin to biodegrade the grease.
There is a need for a bio-augmentation system for use in a waste treatment facility in which the system maintains microorganisms in an active exponential growth and at a predetermined concentration, desirably a maximum concentration, and that further delivers active microorganisms on a continuous or periodic basis into contact with an environment containing wastes for effectively bio-augmenting the biodegradation of the wastes contained in the environment.